Image forming apparatus with a developer circulation mechanism

Abstract

An image forming apparatus includes: at least one retaining member configured to temporarily retain remaining developer remaining on a photosensitive member; a belt arranged opposite to a plurality of photosensitive members; a cleaning device collecting developer on the belt; a remaining developer collecting unit configured to cause the remaining developer retained by the retaining member to be transferred onto the belt via the photosensitive member and thereafter collected by the cleaning device; a circulation mechanism configured to circulate developer between the development chamber and the developer storage chamber; a detector detecting the amount of developer in the developer storage chamber; a determination unit configured to determine if the amount of developer in the developer storage chamber is less than a predetermined amount; and a notifying unit notifying to replace a developer receptacle when the amount of developer stored in the developer storage chamber becomes less than the predetermined amount.

1. An image forming apparatus comprising:
 a plurality of photosensitive members; 
 at least one retaining member positioned in contact with a corresponding photosensitive member and configured to temporarily retain remaining developer remaining on this photosensitive member; 
 a belt arranged opposite to the plurality of photosensitive members; 
 a cleaning device positioned in contact with the belt and configured to collect developer on the belt; 
 a remaining developer collecting unit configured to cause the remaining developer retained by the retaining member to be transferred onto the belt via the photosensitive member and thereafter to be collected by the cleaning device; 
 a plurality of developing units each including a developing roller positioned in contact with a corresponding photosensitive member to supply developer to the photosensitive member, and a development chamber accommodating the developing roller; 
 a plurality of developer receptacles configured to be attached to and removed from corresponding developing units, and each having a developer storage chamber for storing developer; 
 a circulation mechanism configured to circulate developer between the development chamber and the developer storage chamber; 
 a detector detecting the amount of developer stored in the developer storage chamber; 
 a determination unit configured to determine if the amount of developer stored in the developer storage chamber is less than a predetermined amount based on a signal from the detector; and 
 a notifying unit configured to notify a user to replace a developer receptacle when the determination unit determines that the amount of developer stored in the developer storage chamber is less than the predetermined amount, 
 wherein the predetermined amount is set equal to or greater than a remaining amount of developer remaining in the development chamber. 
 
     
     
       2. An image forming apparatus according to  claim 1 , wherein a detection window and a light transmission window are provided opposite to each other at side walls of each developer receptacle with the developer storage chamber interposed therebetween, and wherein the detector comprises:
 a light emitting portion configured to emit light through the detection window; and 
 a light receiving portion configured to receive the light emitted from the light emitting portion through the light transmission window, and 
 the detection window and the light transmission window are positioned higher than a bottom face of the developer receptacle. 
 
     
     
       3. An image forming apparatus according to  claim 1 , wherein the circulation mechanism comprises:
 a partition wall defined by part of walls of the developing unit and the developer receptacle, the partition wall having a first opening through which developer is supplied from the developer storage chamber to the development chamber, and a second opening through which developer is supplied from the development chamber to the developer storage chamber; 
 a feed out carrier mechanism arranged in the developer storage chamber and configured to carry developer in a direction from the second opening to the first opening of the developer storage chamber and to feed developer out from the developer storage chamber and into the development chamber; 
 a supply carrier mechanism arranged in the development chamber and configured to carry developer in a direction from the first opening to the second opening of the development chamber and to supply developer to the developing roller; and 
 a collection carrier mechanism arranged in the developer storage chamber or the development chamber close to the second opening and configured to carry developer from the development chamber to the developer storage chamber. 
 
     
     
       4. An image forming apparatus according to  claim 3 , wherein the collection carrier mechanism is positioned outside an image forming width that is defined within the development chamber. 
     
     
       5. An image forming apparatus according to  claim 4 , wherein the collection carrier mechanism comprises an auger configured to be driven about its rotation axis and to carry developer along the rotation axis. 
     
     
       6. An image forming apparatus according to  claim 5 , wherein bevel gears are provided between the auger and an end of a developer supply member that is accommodated in the development chamber and driven to rotate. 
     
     
       7. An image forming apparatus according to  claim 4 , wherein a rotary driving force transmission mechanism for the feed out carrier mechanism and the supply carrier mechanism is arranged opposite to the collection carrier mechanism with the developer storage chamber and the development chamber interposed therebetween.